In order to make most effective use of the volume of the cavities in a multi-luminal catheter, their cross-section is generally not circular, as shown in FIG. 1(b). The cross-sections of the extension tubes to be connected to the catheter body on the other hand are circular, and if these tubes are connected to the catheter without modification, airtight connections are consequently not obtained. Further, even when the cross-sections of both the catheter lumens and extension tubes are circular, the diameters of the extension tube lumens must necessarily be made smaller to insert the tubes into the catheter lumens. For this reason, a differential arises between the lumens, and gives rise to problems such as increased fluid resistance.
Conventionally, this problem was solved by making the connection through molded pieces of the same shape as the lumens, or by filling the spaces between the catheter lumens and the outer circumference of the extension tubes with adhesive.
If connections were made through molded pieces of the same shape as the catheter lumens, however, the manufacturing cost increased undesirably. If on the other hand the spaces between the inner surfaces of the catheter lumens and extension tubes were filled with adhesive, it was still difficult to obtain a perfectly airtight seal.
Further, in multi-luminal catheters manufactured by the above methods, the joint strength between the catheter body and the extension tubes is inadequate, and the tubes easily fall out of the catheter body in actual use.
This invention therefore aims to provide a multi-luminal catheter wherein extension tubes can be connected easily to the catheter body, and good air-tightness is obtained.